title: Evaluation of the robustness of the preprocessing technique improving reversible compressibility of CT images: tested on various CT examinations.
abstract: OBJECTIVE
  To modify the preprocessing technique, which was previously proposed, improving compressibility of computed tomography (CT) images to cover the diversity of three dimensional configurations of different body parts and to evaluate the robustness of the technique in terms of segmentation correctness and increase in reversible compression ratio (CR) for various CT examinations.
  
  
  METHODS
  This study had institutional review board approval with waiver of informed patient consent. A preprocessing technique was previously proposed to improve the compressibility of CT images by replacing pixel values outside the body region with a constant value resulting in maximizing data redundancy. Since the technique was developed aiming at only chest CT images, the authors modified the segmentation method to cover the diversity of three dimensional configurations of different body parts. The modified version was evaluated as follows. In randomly selected 368 CT examinations (352,787 images), each image was preprocessed by using the modified preprocessing technique. Radiologists visually confirmed whether the segmented region covers the body region or not. The images with and without the preprocessing were reversibly compressed using Joint Photographic Experts Group (JPEG), JPEG2000 two-dimensional (2D), and JPEG2000 three-dimensional (3D) compressions. The percentage increase in CR per examination (CRI) was measured.
  
  
  RESULTS
  The rate of correct segmentation was 100.0% (95% CI: 99.9%, 100.0%) for all the examinations. The median of CRI were 26.1% (95% CI: 24.9%, 27.1%), 40.2% (38.5%, 41.1%), and 34.5% (32.7%, 36.2%) in JPEG, JPEG2000 2D, and JPEG2000 3D, respectively.
  
  
  CONCLUSIONS
  In various CT examinations, the modified preprocessing technique can increase in the CR by 25% or more without concerning about degradation of diagnostic information.
authors.affiliation: Department of Radiology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 300 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707, South Korea.
authors.forename: Chang Ho
authors.initials: CH
authors.lastname: Jeon
authors.forename: Kil Joong
authors.initials: KJ
authors.lastname: Kim
authors.forename: Kyoung Ho
authors.initials: KH
authors.lastname: Lee
authors.forename: Bohyoung
authors.initials: B
authors.lastname: Kim
authors.forename: Tae Ki
authors.initials: TK
authors.lastname: Kim
authors.forename: Bon Seung
authors.initials: BS
authors.lastname: Gu
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Lee
mesh_terms: D007091:Image Processing, Computer-Assisted / Q000379:methods*; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*